1. Field of the Invention
The present invention relates to an image forming apparatus having an intermediate transfer medium, and more particularly, relates to an image forming apparatus which is capable of printing in a short period of time, without image quality defects and without wasteful use of paper and ink.
2. Description of the Related Art
As an image forming apparatus in the related art, an inkjet printer (inkjet recording apparatus) is known which comprises an inkjet printer head (liquid ejection head) having an arrangement of a plurality of liquid ejection nozzles and which records images on a recording medium by ejecting ink (liquid) from the nozzles toward the recording medium while causing the inkjet head and the recording medium to move relatively to each other.
Such an inkjet head of an inkjet printer of this kind has pressure generating units, each comprising, for example, a pressure chamber to which ink is supplied from an ink tank via an ink supply channel, a piezoelectric element which is driven by electrical signals in accordance with image data, a diaphragm which constitutes a portion of the pressure chamber and deforms in accordance with driving of the piezoelectric element, and a nozzle which is connected to the pressure chamber and from which the ink inside the pressure chamber is ejected in the form of a droplet because of the volume of the pressure chamber being reduced by the deformation of the diaphragm. In such an inkjet printer, an image is formed on a recording medium by combining dots formed by ink ejected from the nozzles of the pressure generating units.
It is difficult to remove the ink thus deposited on the recording medium, from the recording medium, and if there is a printing defect in an image recorded on the recording medium by an inkjet printer, it is difficult to perform a correction procedure and ultimately, a recording medium on which printing with defective image quality has been performed must be thrown away. This is undesirable from economical and environmental viewpoints.
Therefore, various methods have been proposed for reducing printing defects.
Japanese Patent Application Publication No. 2005-153521 discloses a method in which it is determined whether an ink ejection port has a failure or not (for example, whether an ink ejection port ejects a desired ink volume or not). If it is determined that the ink ejection port has a failure, then an ink ejection port that is adjacent to the defective ink ejection port and is normal is moved to a position corresponding to the ink ejection section suffering the failure, and additional image formation is then performed by the adjacent ink ejection port, thereby avoiding a printing defect.
Moreover, Japanese Patent Application Publication No. 2003-94615 discloses a method in which the location of the abnormality is identified in an image recorded on a print medium by determining a printing error, and relative movement of the print head is performed in order to carry out printing again.
As described above, various methods have been proposed in order to correct image defects due to nozzle failures, or the like. Both of the inventions described in Japanese Patent Application Publication No. 2005-153521 and Japanese Patent Application Publication No. 2003-94615, have the following correction function. More specifically, recording is once performed on a recording medium; image defects are then determined from the image information recorded onto the recording medium, and the like; the recording medium and the recording head are then moved relatively with respect to each other; and recording is then carried out again using a nozzle having a normal ejection state. Therefore, until the defective nozzles are restored to a normal ejection state by carrying out head maintenance with respect to the defective nozzles, it is necessary to carry out the correction procedure described above for each sheet repeatedly. Accordingly, the time required for printing is twice or more than the time period required for printing when nozzles used are in a normal ejection state. Consequently, printing onto the recording medium requires a large amount of time.
Since it is necessary to move the recording medium and the recording head relatively with respect to each other in such a manner that a nozzle in a normal ejection state reaches a position corresponding to a position suffering an image defect on the recording medium, then a function for achieving this movement must be added to the apparatus, and hence the apparatus becomes large in size and the manufacturing costs increase. Moreover, in cases where the image is not sufficiently corrected as the result even if correction processing of this kind is carried out, the image on the recording medium still suffers image defects, and hence such a recording medium needs to be thrown away eventually.